Electrical music system



March 21, 1933. R, H. RANGER ELECTRICAL MUSIC SYSTEM Filed Nov. 28, 1931Patented Mar. 2l, 1933 UNITED STATES PATENT OFFICE RICHARD HOWLANDRANGER, OF NEWARK, NEW JERSEY, ASSIGNOB TO RADIO CORPO- RATION OFAMERICA, A CORPORATION OF DELAWARE ELECTRICAL MUSIC SYSTEM The presentinvention relates to an electrical music system for producing musicalsounds of Various qualities from electrically generated energy socontrolled as to represent after predetermined selections various notescontaining fundamental and harmonic frequencies for each note in musicalselection.

The present application forms a continuation in part of my copendingapplication Serial No. 417,466, filed December 30, 1929. The aforesaidapplication covers broadly the production of musical sounds and embodiesa system wherein different frequencies corresponding to each of theseveral notes of a musical keyboard are generated electrically and thenso controlled as to reproduce, when selected by an appropriate selectorsystem, any desired musical composition. It has been determined -throughexperiments and practice that musical systems of this type operatesubstantially better when each note of the several reproducedsimultaneously is carried in aseparate amplifier. Consequently, my abovementioned copending application provides for so selecting the variousgenerated frequencies that frequencies corresponding to the fundamentalyand selected harmonics of each note are reproduced or ampliied throughonly a single amplifier, and then these amplified tones or frequenciesmay then be transferred to a suitable load circuit such as a sound reroducer or a wire line. In order to avoid o jectionable effects fromclicking and the like, provision has been made to render the amplifiersoperative only after the frequencies corresponding to the fundamentaland selected harmonics have already been impressed upon the amplifyingcircuits. These general characteristics apply equally well to thepresent invention which is directed principally to the amplifying systemand the manner of producing in the amplifying system different qualityeffects.

The fundamental object of the present in vention is to develop ways andmeans by which the usual thermionic amplifier system may be made toproduce output energies of characteristics which, when reproduced bysuitable sound translating or reproducing apparatus, represent quality'effects simulating the percussion type of instruments. Due to the factthat the percussion type instrument has a changing outputcharacteristic, it has in the past been difiicult to represent this typeof instrument electrically. However, I have found that it is possiblethrough the control of the Voltage applied to the amplifying system tocontrol the amplifier in such manner that the output thereof rises andfalls at a ratecorresponding to and simulating well known percussion`instruments.

In order to illustrate and explain the present invention recourse willbe had to three different types of ercussion instruments which willserve as lllustrative examples of all such types of instruments.Therefore, in this specification reference will be had principally tothe piano, mandolin and vibraphone effects, although it is to beunderstood that other similar effects may be produced in similar manner,and the disclosure should, therefore, be construed broadly as coveringall such types of instruments generically.

Still other objects of my invention are to produce the percussion typeeffects in electrical music instruments without any complicatedelectrical switching arrangements and to` arrange the system so that itwill respond instantly to the operators choice of quality effects as maybe controlled by the usual tilting tablets or push buttons arranged onthe console of an organ, for example, to enable the operator or organistto select the quality effect desired.

Still other objects of the invention are to provide in a simple manneran arrangement for producing the percussion effects which is relativelysimple in its construction and arrangement of parts, a system which issubstantially fool-proof, which will not require any great attention onthe part of the operator, and which may be combined with electricalorgans of the general type disclosed in my above named copendingapplication with a minimum expense. c

Still other and further objects of the invention will become apparentand at once sug` gest themselves to those skilled in the art to whichthe invention relatesv by considering the following specification andclaims in connection with the accompanying drawing, wherein:

Fig. 1 represents a suitable form of amplifier for amplifying generatedelectrical frequencies corresponding to a single note to be played atany instant; and,

Figs. 2-A, 2-B and 2-C represent a series of curves plotted withintensity against time to represent the output from the amplifyingsystem for different quality effects. Of this group Fig. 2-A representsthe piano effect; Fig. 2-B represents a Vibraphone effect; and Fig. 2--Crepresents a mandolin or pick instrument effect.

Now making reference to the accompanying drawing, and considering thesame as representing only a single one of a number of amplifiersnecessary to produce a number of musical sounds simultaneously, asWasdis-` closed in my aforesaid copending application, the variousreference numerals correspond for the most part to identical referencenumerals in the original application in order to permit ease ofunderstanding the present invention. It should, however, be borne inmind that the amplifying system herein represented will produce only onenote including the fundamental and selected harmonies at any instant,

and for the production of .a complete'series p of notes simultaneouslyplayed the entire system shown herein would have to be duplicated anumber of times, for example', six to twelve times, depending upon thenumber of notes it is desired to reproduce simultaneously.

- By t-he acco-mpanying drawing, conductors 115, 116, 117, 118 and 119connect the amplifying system with suitable tone selection relays whichin turn are connected to a source of tone frequency energy (not shown)The energy impressed upon the various conductors 115 through 119inclusive is then transferred through suitable transformers 140, 141,142, 143, 144 and 145 to a thermionic amplifier system comprising aplurality of thermionic amplifying tubes 153, 154, 155,

. 156, 157 and 158 having their outputs connected in parallel. Tocont-rol the intensity of the various frequencies impressed upon theamplifiers, a number of resistor elements 146, 147, 148, 149 and 150 hasbeen provided in series with the primary Winding of each o f thetransformers 141 through 145 inclusive.

In the present instance, let it be supposed that amplifying tubes 153and 154, as energized through transformers and 141 respectively, areused for the purpose of amplifying the fundamental frequency. In thisinstance it should be noted that transformer 140 impresses thefundamental with full strength or amplitude upon the amplifying tube153, Whereas the transformer 141, for example, impresses the samefundamental frequency upon the amplifier 154 in reduced intensity, sothat the net amplification may be some value greater than unity wheredesired. Similarly, transformers 142 through 145 inclusive, ascontrolled by resistors 147 through inclusive respectively, impress thevarious selected harmonic frequencies with controlled amplitudessuitable for representing the desired quality effects upon theamplifiers through 158 inclusive. The primary windings of thetransformers 140 through 145 inclusive are'suitably grounded throughconductor-'151 connected to ground at 152 in order that only a singleWire system may be necessary to impress the various tones upon the inputof the amplifier. To control the amplification in desired manner,suitable biasing means such as the C batteries 159 may be connected inthe input circuit of each of the amplifiers 153 through 158 inclusive.The filaments of the amplifiers may be supplied with energy through thevariable resistor elements 163 Which connect with lthe positive terminalof the source of filament energy, and the opposite terminal of thefilament may be suitably grounded at for example.

As was above stated, amplifiers 153 through 158 inclusive have theiroutputs con'- `nected in parallel through a conductor 166 connected inseries with a choke to a ter minal 164 of positive potential +B suitablefor energizing the plate electrodes of each tube. In shunt with thechoke coil is a condenser element 168 and the primary Winding 169 of atransformer 170 to the secondary Winding 171 of which is connected apair of ther-mionic amplifiers 172 and 173 in push pull. Each of theseamplifiers may be biased in any suitable manner by means of a biasbattery such as 174, and the filaments thereof may be connected toground, for example, at 17,5. The output energy from the push pullamplifiers 172, 17 3 may be then transferred through the primary Winding194 of transformer 195, and then picked up in the secondary Winding 198of the transformer. To supply plate potential to the amplifiers 172 and173, a connection is made to the midpoint 193 of the primary Winding 194of the transformer. It is at this point that the con'- trol effectA forproducing the various qualities to represent the percussion instrumentswill be introduced, but for the purpose of completing the description ofthe manner in which the tones as amplified are transferred to the loador utilization circuit the remaining portion of the amplifying systemwill first be described, after Which the manner in lli) which thevarious quality effects are produced In a manner similar to that exlained with the preceding stage of push pul amplification, the inputcircuits of these amplifiers may be suitably biased by means of resistor205 and biasing battery connected thereto. The filament circuits ofthese amplifiers may be supplied from a source of heating currentconnected to one side of the filament at 208, and to the other side ofthe filaments through potentiometer 207 and then to ground as at 209.The output energy from the amplifiers 199 and 200 is'then fed through apair of conductors 242 and 241 to the primary winding 243 of atransformer 244, from the secondary winding 246 of which the usefulamplified output is connected with a load circuit connected at terminals247 and 248. This load circuit may be the usual type of sound reproducerin the event that it is desired to hear the music produced locally, orwhere it is desired to broadcast the produced energy, the terminals 247and 248 may connect directly with a transmitter for transmission overwire or radio circuits, or the terminals may connect with any suitableform of land line to carry the energy to the point of transmission.

In my aforesaid application Serial No.

' 417,466, the desirability of connecting the tones for reproductionwith the amplifying system prior to the time when the amplifier wasrendered operative was explained, and. in addition, the aforesaidapplication disclosed ways and means by which the amplifier system wasrendered operative immediately after the tones had been impressedthereon. NOW, according to the present invention, the same generalfeatures hold true. However, in the original case, the amplifiers wererendered inoperative by a removal of the plate potential therefrom atall times except When tones were keyed in the input circuit, and it wasonly at these times that the amplifier could function in the normalmanner. According to the present application, instead of having theplatesupply energ disconnected except when the tones are keye the platesupply connected to theterminal 184 is normally connected'todthe platesof the push pull connected amplifying tubes 172 and 17 3 through thearmature 203 of the relay R40 resting against the contact 187 andconnecting through a conductor 188 to the conductor 210 at a point 630.It will be seen that with the relay R40 unen'ergized, due to the lack ofany impressed voltage being impressed thereon through the line 177 whichconnects with the keying contact of the selector system, the platesupply energy is then grounded through a conductor 189 connected to thearmature 201-of the relay R40 and grounding through a resistanceconnection between the ground point and the contact 627 ofthe relay R40.Therefore, While plate potential is being supplied to the tubes 17 2 and17 3, they are nevertheless maintained in an inoperative state as in theaforesaid applicaion.

Now sup ose that a note of the ke board is depresse ener 'from asuitable eyin contact of the se ector relays (not shown? is suppliedthrough conductor 177 so as to flow through the terminal point 178, theconductor 179 to the armature 202 of the relay R40 from whence it passesthrough the contact 180 and the conductor 181 through the relay windingR40 and thence to ground. As soon as the relay Winding R40 becomesenergized, all of the armatures 201, 202 and 203 1mmed1ately move to theleft from the position shown, and the contact between the armature 202and the terminal 180 is at once broken. However, when this happens, thesame energy that was supplied through the conductor 177 then flows fromthe terminal 178 through the resistor 188 and the conductor 181 throughthe winding R40 to ground, so as to form a holding current just suicientto maintain the relay armatures 201, 202 and 203 over against their leftside cgntacts or in the opposite position from that s own.

To provide a suitable arrangement bywhich late potential may be suppliedto the tubes l 2 and 173, itis proposed to arrange the relay armatures201, 202 and 203 in such a manner that when the relay R40 becomesenergized the armature 201 will be first to open. This will then removethe ground' from the lead 210 and permit the plates of the tubes 172 and173 to receive normal plate potential supply through the armature 203and the contact 187 as supplying energy to the conductor 210 through theline 188. The operation of the armature 201 to occur first may 4beprovided in any suitable manner, for example, by merely bending-thearmature 201 slightly so that it leaves its contact 627 prior to thetime when the armatures 202 and 203 become disengaged from the contacts180 and 187 respectively upon energization of the relay R40.

Now, a very short time interval after the opening of the armature 201,the armature 203 also opens and the +B voltage supplied from theterminal 184 reaches the tubes 172 and 173 through a point 626connecting through conductor 626 to the contact terminal 619 of therelay R40, and through the armature 612 of this relay the platepotential supplied at the terminal 184 is directed through the conductor210, the choke coil 197 to supply the plate potential in the usualmanner, assuming, of course, that none of the special quality effectswhich form the basis of this invention are desired. With the relay R40so adjusted as to provide the seuence of operation above set forth, theconensers or capacity elements 600 and 625 may be fully charged beforethey are used to supply the plates of the tubes 17 2 and 17 3 withvenergy in a manner to be hereinafter described.

Assume now, for example, that a piano effect is desired from the system.This e'l'ect 5 has been represented in a general form graphically byFig. 2-A, wherein, when `plotting intensity against time, 1t 1s seenthat the tone immediately rises to a full value and then fades out in amanner quite characterl0 istie of the usual piano. When the piano effeetis desired, the switch 624 serving to represent a tilting tablet or pushbutton on the organ console is closed and this then causes the relay R46to become energized by a flow of current from the switch 624 through therelay, and, as this happens, the armatures 611 and 612 move to the rightfrom the position shown. This serves to break the contact alreadyestablished between the contact point 619 and the armature 612 'so as tointerrupt the supply of plate potential-from the source 184 to the tubes172 and 17 3. In the first momentary connection of the plate supply forthe tubes 172 and 173 from the point 184, the capacity element 600 willbecome ycharged through the conductor 188, the contact polnt 630, theconductor 210, the relay armature 610, the contact 618 connected to thearmature 606 of the relay R43 and the contact 613 connecting to one sideof the capacity element 600. lVhen the plate supply is disconnectedfollowing the opening of armature 203 at a time when the relay R40 isenergized by the depression ofa key caus- 177, as above explained, thecapacity element or condenser 600 then takes over the task of supplyingplate potential to the plates of the tubes 172 and 173.

As will be appreciated, there is a logarithmically decaying voltagesupplied to the plates of the tubes 172 and 17 3 through the contact613, the armature 606 of the relay R43, through contact 618, througharmature 610 of the relay R45, and thence through the conductor 210 tothe plates. The tone produced from the push pull connected amplifiers172and 173 thus fades out in amanner characteristic of pianos.

The usual type of percussion effect, such as the vibraphone eifect, maybe produced in a manner quite similar to the piano eilect by closing,for example, the tilting tablets or switches 622 and 624 simultaneously,bearing in mind that the piano eiiect as produced by the switch 624 isused jointly with a second effect produced by operation of the switch ortilting tablet 622. Through the closure of the switches 622 and 624,relavs 11 and R46 respectively become energizedy by a flow of currenttherethrough from the switch element to the opposite side of the relay,and thus cause the armatures 602 and 612 respcc tively to be moved tothe right from the position shown y ing current to'flow through theconductor of current in a manner already explained in y my above namedcopending application. In the aforesaid copending ap lication, a rubbertube arrangement was il ustrated for periodically decreasing the valueof the plate potential supplied, and also there was disclosed a systemfor varying the filament current supplied to the tubes so that, in eachinstance, the output of the amplifying tube system was varied betweencertain predetermfned limits at al chosen rate.

Assume now that theconductor 626 oonnecting with the armatures 602 and604 of relays R41 and R42 respectively is supplied with energy orpulsations of currents from a tremolo device, so that the current flowtherethrough rises and falls in intensity at a suitable rate. As therelay R,u has been ener-- 'gized to move the armature 602 to the rightfrom the position shown by the closure 'of the l switch 622, thefluctuating current supplied from the tremolo through the conductor 626then passes through the contact point 614 to the relay winding RA13 soas to close the armatures 605 and 606 respectively over against theirright side contacts from the position shown. at arate corresponding tothe, tremolo rate, and thus alternately break the conta-ct between thearmature 606 and the contact point 613.

Assume now that a note on the keyboard has been played and. that thecapacity or condenser element 600 is energized as above explained forthe production of the piano effeet. During the periods when the relayR43 is open (the position shown), the diminishing charge` on'thecapacity element 600 supplies the plate energy for the tubes 172 and 173as before, but during those periods when t-he relay .R4G is energized,the connection is broken at the Contact point 613 and the platepotential is then supplied only from the charge on a much smaller platefilter c'ondenser 197. lThis is illustrated graphically by Fig. 2-B,wherein, through plotting intensity against time, it is seen that theoutput rises to a. substantial peak, then decays lvery gradually, thenmore sharply, after which it rises again to a predetermined point, afterwhich the same process is repeated. The tone thus produced in the loadcircuit or utilization circuit connected to the output terminals 247 andv248 of the system follows the characteristic vibraphone curve.

A mandolin elect may be produced in the system in a manner closelyanalogous to that already explained except to produce this effect theswitches or tilting tablets 623 and 624 are closed simultaneously, so asto cause the relays R42 and R48 respectively to move the armatures 604and 612 to the right from the position shown. As is seen from thedrawing, the relay amature 603 when moved over against its right sidecontact will have positive energy connected to the right Side contact asindicated by the plus sign dlrected through itand the conductorconnecting with the relay R,5 so as to cause this relay to becomeenergized and move the armatures 609 and 610 respectively to the rightfrom the positionshown so that they rest upon the right side contacts620 and 617.

Similarly, as the armature 604 has been moved to the right over againstthe right side contact 615 by the energization of relay R42 through theclosure of the switch or tilting tablet 623, the same pulsations oftremolo current above explained in connection with the Vibraphone effectare supplied through theconductor 626 to the relay armature 604 andthrough the contact 615 cause the relay R,4 to become energizedperiodically so as to vibrate the armatures 607 and -608 at a ratecorresponding to the tremolo rate. As the armature 608 vibrates at thetremolo rate, contact is periodically broken with the contact point 615and made with the contact point 616, and vice versa.

During the periods when the relay R44 is open, the plate Y of thecapacity element 625 may receive a positive charge from the source ofplate potential connected at 184 through the point 626, the conductor626', the contact point 619, the armature 609, the contact point 620,the contact 615 of tle relay R44 and the armature 608 thereof. However,when the relay R44 is closed, on the other hand, the capacity element625 is short-circuited through the armature 608, the contact 616connecting to the opposite side of the capacity element so as to cause apositive 'charge on the plate X. v

Now, after a note has been played and the direct positive connection tothe plates of the tubes 172 and `173 broken, the plate X of the capacityelement 625 will, during those periods when the relay R44 is open,supply the plates of these tubes through the contact 617. the relayTarmature 610 and the lead 210, with positive potential. During theperiods when the relay R44 is closed, the plates of the tubes 172 and173 will be maintained at positive potential by means of the filtercondenser 197 connected in series with the lead 210 while the potentialof the plate X of the condenser 625 is restored by connection throughthe armature 608 yand the contact 616 to the plate Y thereof, which has,of

course, been maintained at positive plate p0- tential during the periodswhen the relay R44, is open. The. effect of this alternate control ofthe plate potential by means of the capacity elements 197 and 625 is toproduce a voltage upon the plates of the tubes 172 and `173 whichproduces in the utilization circuit connected to the terminals ,247 and248 of the system an output varying as indicated by the intensity-timecurve shown by Fig. 2-C.`

From the above, it is quite apparent that with a system of the typeherein disclosedcapacity elements have been associated with the outputcircuits of a plurality of amplifiers in such a manner that, by theapplication of definite voltages as supplied from a voltage source usedto supply the plate potential for the amplifiers, they function when akey of the system is depressed to break the complete connectioninstantly in such a manner that the amplifier only works from platecurrent in thc condensers which can be dissipated logarithmically insuch a manner as to produce the effect desired.

By the above description, it should be recognized, of course, thatapplicant has made no effort to show a complete system, but for apractical instrumentality it should be understood that the entirearrangement herein disclosed is duplicated for a series of independentand separate amplifiers. Of course, to simplify the arrangement, thereis preferably only a single tilting tablet or switch such as 622, 623 or624 for the entire system, and these may be made to work separately forall amplifiers. Furthermore, where desired of course, it is possible toconstruct the system so that the various amplifiers may be provided withdifferent quality effects, and in such cases it is desirable to have thedifferent switches for the production of the different quality effectsWork independently. Also, for the purpose of controlling the tremolostrength, I have provided a pedal connection which serves to vary theresistance 629 between predetermined limits, .and thus to control thestrength of the useful tremolo effect as supplied through the conductor628.

From the above description it will be apparent that many modificationsand changes may be made without departing from the spirit and scope ofthe invention, and therefore I believe myself to be entitled to coverany and all of thcse'modifications as would suggest themselves to thoseskilled in the art to which the invention relates, and have thereforedefined the invention in its broadest terms by the following claims,wherein I claim and desire to secure by Letters Patent of the UnitedStates the following:

1. In an electrical music system having electrical energy of frequenciescorresponding to each note on the musical scale separately generated,the combination which comprises an independent amplifier for amplifyingthe electrical frequencies corresponding to each musical note to bereproduced, and means to supply operating voltages of predeterminedvarying values to each amplifier for varying the output energy thereofat a rate to cause the simulation of percussive instrument effects.

output energy thereof at a rate to cause the simulation of percussiveinstrument effects. 3. In an electrical music system having electricalenergy of frequencies corresponding to each note on the musical scaleseparately generated,l the combination which comprises an independentamplifier for ainplifying the electrical frequencies corresponding toeach musical note to be reproduced, and capacity means operativelyassociated with the output circuit of each amplifier to supply operatingvoltages of p redetermined varying values to eachampliiier for varyingthe output energy thereof at a rate to cause the simulation ofpercussive instrument effects.

4. In an electrical music system having enerating means for producingelectrical requencies corres onding to each of the several notes throngout the musical scale, the

' combination which comprises means for independently amplifying thegenerated frequencies corresponding to each note to be reproduced, autilization circuit for each of the amplified frequencies, and means forvarying the strength of the amplified frequencies supplied to theutilization circuit in a manner to, simulate the rise and fall ofaudible energy from percussive instruments.

5. In an electrical music system having means for electricallygenerating, amplifying and audibly reproducing tone frequenciescorresponding to ,the several notes throughout the musical scale, meansfor varying the intensity of the audibly reproduced tone frequenciesbetween predetermined maximum and minimum intensities, said variationoccurring at a relatively slowly changing logarithmic rate for changesbetween predetermined maximum and minimui'n intensities and at arapidly. increasing rate for each change from minimum to maximum.

6. In an electrical music system having a series of alternators forproducing electrical frequencies corresponding to the consecutivenotesof a musical scale, a plurality of amplifiers for amplifying thevarious produced` frequencies'in accordance with a predeterminedselection thereof, means for controlling the intensity of each of thefrequencies impressed upon said amplifiers in accordance with the tonequality desired, capacity means associated with the amplifying systemsfor supplying definite voltages thereto during periods when each amliier is rendered operative and providing or a adual dissipation ofenergy from the ampli er during said lperiods, and a sound reproducercoordinate with each of said am lifying systems for converting theamplifie energy into audible ener 7 In an e ectrical music system havina plurality of sources for generating electrical frequenciescorresponding to the fundamental and other partial frequencies for eachnote throu hout themusical scale, the combination of a plurality ofamplifiers each arranged to amplify at any instant the frequenciescorresponding to a single note only, means for maintaining a portion ofeach amy plifier circuit during periods of inoperativeness at groundpotential, means for keyin each amplifier circuit independently witelectrical frequencies corresponding to a. note to be reproducedthereby, and a lurality of relay means associated with t e arnplifiercircuits for controlling the operative characteristics thereof to causeva fluctuating output therefrom which decreases in intensitylogarithmically to simulate percussive instrument effects.

8. In an amplifying circuit for electrical music devices, a lurality ofvacuum tubes serving to ampli y frequencies corresponding to the severalynotes on the musical scale, means for applying operating potentials tosaid amplifying circuit, capacity means associated with said supplycircuits and adapted to become charged throu h the application of saidpotentials, a plurality of relay means for rendering said amplifiersoperative in accordance with predetermined note selections, a secondplurality of relays for controlling the quality effects from the outputof the said amplifiers, said second series of relays being adapted tocontrol the discharge of energy from said capacity elements to produce.a logarithmically changing intensity output from said amplifiers tosimulate percussive instrument effects.

9. In an amplifying circuit for electrical music devices, a plurality ofvacuum tubes serving to amplify frequencies corresponding to the severalnotes on the musical scale, H5

means for applying operating potentials to said amplifying circuit,capacity means associated with said supply circuits and adapted tobecome charged through the application of said potentials, a pluralityof relay means for rendering said amplifiers operative in accordancewith predetermined note selections, a second plurality of relays forcontrolling the quality effects from the output of the said amplifiers,said second series of relays being adapted to control the discharge ofencrgy from said capacity elements to produce a logarithmicallydecreasing intensity output from said amplifiers to simulate percussiveinstrument effects.

10. n an amplifying circuit for electrical music devices, a plurality ofvacuum tubes serving to amplify frequencies corresponding to the severalnotes on the musical scale, means for applying operating potentials tosaid amplifying circuit, capacity means associated with the potentialsupplying circuits and adapted to become charged through the applicationof said potentials, a plurality of relay means for rendering saidamplifiers operative in accordance with predetermined note selections, asecond plurality of relays for controlling the quality effects from theoutput of the said amplifiers, said second series of relays beingadapted to control the discharge of energy from said capacity elementsto produce a logarithmically changing intensity output from saidamplifiers to simulate percussive instrument effects, and a tremolocontrol device for varying the supplied potentials between predeterminedlimits for causing during the periods when said ampliers are renderedoperative periodic increases in the charges upon said capacity elements,whereby after predetermined periods of logarithmically changingintensity outputs the intensity of output is rapidly varied in anopposite direction for a repetition of the preceding intensity change soas to simulate percussive instrument effects.

11. In an amplifying circuit for electrical music devices, a pluralityof vacuum tubes serving to amplify frequencies corresponding to theseveral notes on the musical scale, means for applying operatingpotentials to said amplifying circuit, capacity means associated withthe potential supplying circuits and adapted to become charge-d throughthe .application of said potentials, a plurality of relay means forrendering said amplifiers operative in accordance with predeterminednote selections, a second plurality of relays for controlling thequality effects from the output of the said amplifiers, saidsecond-series of relays being adapted to control the discharge of energyfrom said capacity elements to produce a logarithmically decreasingintensity output from said amplifiers to simulate percussive instrumenteffects, and a tremolo control device for varying the suppliedpotentials between prcdetermined limits for causing during the periodswhen said amplifiers are rendered operative periodic increases in thecharges upon said capacity elements, whereby after predetermined periodsof logarithmically decreasing intensity outputs the intensity of outputis raised rapidly for a repetition of the decrease in intensity soI asto simulate percussive instrument effects.

RICHARD HOWLAND RANGER.

